Semiconductor device

ABSTRACT

A semiconductor device having a wafer level chip size package may include a semiconductor substrate having an integrated circuit formed thereon; a plurality of electrode pads formed on the semiconductor substrate; at least one rewiring layer which may include rewiring formed adjacent to the plurality of electrode pads; and a plurality of external electrodes formed on the rewiring layer. The plurality of electrodes and plurality of external electrodes may be sectioned and arranged in four areas having the same shapes. Each area may include a first group of N number of external electrodes arranged along an edge of the semiconductor substrate, a second group of (N−2) number of external electrodes arranged inside the first group of external electrodes, and a plurality of (2N−2) number of electrode pads arranged between the first and second groups of external electrodes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of the U.S. patentapplication Ser. No. 11/238,189 filed Sep. 29, 2005, the contents ofwhich are incorporated by reference herein in their entirety, priorityto which is claimed under 35 U.S.C. § 120. U.S. application Ser. No.11/238,189 claims the benefit of the date of the earlier filed JapanesePatent Application No. JP 2004-283167 filed on Sep. 29, 2004, thecontents of which are incorporated herein by reference, and priority towhich is also claimed herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a semiconductor device, and more particularlyto a semiconductor device having a chip size package (hereinafter,referred to as CSP) structure.

2. Description of the Related Art

With the recent miniaturization of information terminals such as acellular phone and a personal digital assistance (PDA), miniaturizationof semiconductor devices to be used inside, such as LSIs, has been inincreasing demand. Under such circumstances, attention has been given toa packaging technology called ball grid array (BGA) structure.

Unlike conventional quad flat package (QFP) structures in which leadframes are used to connect semiconductor devices to a substrate, the BGAstructure achieves substrate connection via terminals called solderbumps or solder balls which are formed on the surfaces of thesemiconductor devices. According to this BGA structure, externalconnection terminals can be formed over the entire surfaces ofsemiconductor devices. This can eliminate the need for lead framesaround the components, allowing a significant reduction in packagingarea.

By using this BGA structure, there has been developed a packagingtechnology called chip size package (CSP), in which the area of asemiconductor chip and the packaging area of the same are approximatelyequal. There has also been developed a technology called wafer level CSP(WL-CSP), in which solder bumps are formed directly on semiconductorchips without any substrate. This promotes the miniaturization ofsemiconductor devices (see Japanese Patent Laid-Open Publication No.2003-297961).

A semiconductor device to which this CSP technology is applied hasexternal connection terminals made of solder bumps, which are oftenarranged systematically on the surface of the semiconductor device forthe sake of connection with a printed-circuit board as shown in FIG. 1of the above-mentioned patent document.

Meanwhile, given a semiconductor substrate having a semiconductorintegrated circuit formed thereon, electrode pads intended for signalinput and output are often arranged along the periphery of thesemiconductor integrated circuit as is the case with the QFP structure.The electrode pads formed on the periphery of this semiconductorintegrated circuit are routed by a rewiring layer to the positions ofsystematically-arranged solder bumps for the sake of electricconnection.

Under the circumstances, the inventor has become aware of the followingproblem. FIG. 5 shows an example of the layout of electrode pads andsolder bumps on a semiconductor device 500 having the CSP structure,showing the problem of the present invention. Electrode pads 10 arearranged along the periphery of the semiconductor device 500. Solderbumps 20, or external lead electrodes, are also arranged systematicallyon the semiconductor device 500. Rewiring 30 routes signals from thepositions of the electrode pads 10 to the positions of the solder bumps20, or external lead electrodes, for respective electric connections. Asin FIG. 1 of the patent document, the solder bumps 20 are arranged onthis semiconductor device 500 inside the electrode pads 10.

Now, focus attention on the electrode pads 10 a and 10 b, and the solderbumps 20 a to 20 d. The electrode pads 10 a and 10 b are connected tothe inner solder bumps 20 a and 20 b, respectively, out of the solderbumps arranged in two rows. In this case, rewiring traces 30 a and 30 bmust be laid so as to pass between the solder bumps 20 c and 20 d.

As a result, the rewiring traces 30 a and 30 b have greater lengths thanthat of a rewiring trace 30 c to be connected with the outer solder bump20 c. This causes differences in the rewiring length, which canadversely affect circuit characteristics including resistances andinductances.

In order to lower these resistances and inductances, it might be desiredto put the solder bumps 20 closer to the chip edges. Nevertheless, thedistance between a chip edge and a solder bump 20, designated by d inthe diagram, is restricted by the rewiring. The reason is that thedistances from the rewiring traces to the respective electrode pads andsolder bumps must be rendered greater than a predetermined distancewhich is determined by design rules on the semiconductor manufacturingprocess of the semiconductor device 500. For example, trying to put thesolder bump 20 c closer to the chip edge of the semiconductor device 500has limitations since the rewiring trace 30 a and the solder bump 20 c,and the rewiring trace 30 a and the electrode pad 10 b, must be spacedwider than a certain distance determined by the design rules.

Consequently, useless gaps required for the rewiring layout appear onthe periphery of the semiconductor device 500 outside the solder bumps20. There has thus been the problem of an increased chip size.

SUMMARY OF THE INVENTION

One of the aspects of the present invention relates to a semiconductordevice. This semiconductor device comprises: a semiconductor substratehaving an integrated circuit formed thereon; a plurality of electrodepads formed on the semiconductor substrate, being intended for input andoutput of signals between the integrated circuit and an externalcircuit; and a plurality of external electrodes connected to theplurality of electrode pads via rewiring, the external electrodes makingconnection terminals for the external circuit. The plurality of externalelectrodes include a first group of external electrodes arranged alongan edge of the semiconductor substrate and a second group of externalelectrodes arranged inside the first group of external electrodes. Theplurality of electrode pads are arranged between the first group ofexternal electrodes and the second group of external electrodes, and areeach connected to an external electrode included in either the firstgroup of external electrodes or the second group of external electrodesvia the rewiring.

The “electrode pads intended for input and output of signals between theintegrated circuit and the external circuit” refer to electrode padsthat supply signals to, lead out signals from, or ground or otherwisetreat the circuit elements constituting the integrated circuit. The“external electrodes” refer to electrodes that function as terminals forconnecting to the external circuit, such solder bumps, solder balls, orposts.

According to this aspect, the plurality of electrode pads are arrangedbetween the first group of external electrodes and the second group ofexternal electrodes. Consequently, the external electrodes included ineither of the groups can be connected by approximately the samedistances of rewiring. Since the lengths of the rewiring traces have animpact on the wiring resistances and inductances, it is possible tosuppress variations in the electric characteristics. In addition, sincethe rewiring need not be routed outside the first group of externalelectrodes, it is possible to put the first group of external electrodescloser to the outer edges of the semiconductor device withoutconstraints from the layout of the rewiring. This can suppress anincrease in chip size.

The integrated circuit may include: input/output circuits to beconnected to the plurality of electrode pads, being arranged on anoutermost periphery of the semiconductor device; and a functionalcircuit arranged near the center of the semiconductor substrate. Theplurality of electrode pads may be arranged between the input/outputcircuits and the functional circuit.

The “input/output circuits” refer to protective elements which areconnected with the respective electrode pads and protect internalcircuit elements, and circuits which have a predetermined circuitconfiguration and size, such as an input/output buffer. Since theinput/output circuits are disposed to the space above the integratedcircuit, appearing outside the electrode pads, it is possible to improvethe use efficiency of space. This allows a further reduction in chipsize.

The plurality of electrode pads may have a minimum spacing generallyequivalent to an integral multiple of the minimum spacing of theplurality of external electrodes.

With twice the spacing in particular, two adjoining external electrodesout of the first group of external electrodes and two out of the secondgroup of external electrodes are located near respective correspondingfour electrode pads. This allows economic, efficient rewiring.

The first and second groups of external electrodes may be arrangedsystematically at regular intervals. The systematic arrangement of theexternal electrodes facilitates determining the layout of the electrodepads and the rewiring.

The semiconductor device may further include an insulating film formedover the electrode pads, the insulating film having openings atlocations above the electrode pads. The rewiring may be formed on thisinsulating film.

Another aspect of the present invention is also a semiconductor device.This semiconductor device comprises: a semiconductor substrate having anintegrated circuit formed thereon; a plurality of electrode pads formedon the semiconductor substrate, being intended for input and output ofsignals between the integrated circuit and an external circuit; and aplurality of external electrodes connected to the plurality of electrodepads via rewiring, the external electrodes making connection terminalsfor the external circuit. The plurality of external electrodes include afirst row of group of external electrodes arranged linearly, and asecond row of group of external electrodes arranged linearly in parallelwith the first row of group of external electrodes. Some of theplurality of electrode pads are located in an area interposed betweenthe first and second rows of groups of external electrodes, and are eachconnected to one of the external electrodes in either the first orsecond row of group of external electrodes by means of the rewiring.

According to this aspect, the electrode pads are located in the areainterposed between the external electrodes which are arranged in twoparallel rows. The connections to the two rows can thus be made byalmost the same distances of rewiring.

The plurality of electrode pads may be arranged linearly in parallelwith the first and second rows of groups of external electrodes. Sincethe plurality of electrode pads are arranged linearly, the externalelectrodes and the electrode pads are situated in parallel with eachother. This can simplify the rewiring connections.

The first row of group of external electrodes, the second row of groupof external electrodes, and the plurality of electrode pads may bearranged systematically at regular intervals. The systematic arrangementof these also results in systematic layout of the rewiring. The rewiringconnections can thus be simplified further.

The first or second row of group of external electrodes may have aminimum spacing generally equivalent to an integral multiple of theminimum spacing of the plurality of electrode pads.

It is to be noted that any arbitrary combination or rearrangement of theabove-described structural components and so forth are all effective asand encompassed by the present embodiments.

Moreover, this summary of the invention does not necessarily describeall necessary features so that the invention may also be sub-combinationof these described features.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings which are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalFigures, in which:

FIG. 1 is a plan view of a semiconductor device according to a firstembodiment;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1;

FIG. 3A to 3D are plan views of the semiconductor device according to asecond embodiment, showing part of the layout of electrode pads, solderbumps, and rewiring;

FIGS. 4A and 4B are plan views of part of the semiconductor deviceaccording to a third embodiment in a manufacturing phase; and

FIG. 5 shows an example of the layout of electrode pads and solder bumpson a semiconductor device having a CSP structure, explaining the problemof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described based on preferred embodiments whichdo not intend to limit the scope of the present invention but exemplifythe invention. All of the features and the combinations thereofdescribed in the embodiment are not necessarily essential to theinvention.

FIRST EMBODIMENT

FIG. 1 is a diagram showing a semiconductor device 100 according to anembodiment of the present invention, as viewed from the electrode-padside. The semiconductor device 100 has a CSP structure. In the diagram,the semiconductor device 100 includes: a plurality of electrode pads 10for inputting and outputting signals from/to exterior; solder bumps 20for making external lead electrodes; and rewiring 30.

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1. Thissemiconductor device 100 has the WL-CSP structure in which externalconnection electrodes are formed directly on its semiconductor substrate40. The semiconductor device 100 includes the semiconductor substrate40, a protective film 42 for passivation, the electrode pads 10, therewiring 30, posts 48, the solder bumps 20, and a sealing resin 50.Semiconductor integrated circuits including such devices as a transistorare formed on the top of the semiconductor substrate 40, and areprovided with the electrode pads 10 intended for signal input andoutput. The electrode pads 10 are typically made of such a material asaluminum.

The protective film 42 is a nitrided silicon film or the like, which isformed to have openings above the electrode pads 10. The rewiring 30 ismade of copper, aluminum, gold, or the like. The rewiring 30 routessignals from the electrode pads 10 to the positions of the solder bumps20, which are the final positions of formation of the external leadelectrodes, and connects the same to the posts 48. The columnar posts 48are made of gold, copper, or the like, and establish electric connectionbetween the solder bumps 20 and the rewiring 30. Incidentally, aninsulating layer made of an oxide film, polyimide, or the like may alsobe formed over the protective film 42, in which case the rewiring 30 isformed thereon.

Return now to FIG. 1. In FIG. 1, the solder bumps 20 are arranged in tworows along the periphery of the semiconductor substrate 40. Theelectrode pads 10 are arranged inside the outermost solder bumps so asto be interposed between the two rows of solder bumps.

Each of the traces of the rewiring 30 is extended from an electrode pad10, and is connected to any one of the outermost solder bumps 20 or theinner solder bumps 20.

According to the present embodiment, the outermost solder bumps and theinner solder bumps both can be connected with the electrode pads 10 byapproximately the same distances of rewiring. In addition, since therewiring 30 does not fall outside the outermost solder bumps, theoutermost solder bumps can be located close to the edges of thesemiconductor substrate 40 without constraints from the layout of therewiring 30 as far as allowed by the rules of the manufacturing process.It is therefore possible to suppress an increase in chip size.

SECOND EMBODIMENT

The semiconductor device 100 according to this second embodiment ischaracterized by that the solder bumps 20 and the rewiring 30 arearranged systematically. FIGS. 3A to 3C show part of the layout of theelectrode pads 10, the solder bumps 20, and the rewiring 30 on thesemiconductor device 100 according to the present embodiment.

Each of the areas shown in FIGS. 3A to 3C represents one of four areas300 a to 300 d having the same shapes, corresponding to the respectivesides of a rectangular, shown by the broken lines in FIG. 3D. In FIGS.3A to 3C, both the electrode pads 10 and the solder bumps 20 arearranged at regular intervals.

In FIGS. 3A and 3B, the solder bumps 20 are arranged linearly in twoparallel rows at regular intervals. The electrode pads 10 are arrangedlinearly in the area interposed between the two rows of solder bumps.The electrode pads 10 are spaced at approximately ½ the spacing of thesolder bumps 20.

With the traces of rewiring 30, the respective electrode pads 10 areconnected to outer and inner ones out of the two rows of solder bumps 20alternately in generally the same distances.

In FIG. 3C, the electrode pads 10 are also arranged linearly in twoparallel rows. Each of the electrode pads 10 is connected to a nearestsolder bump 20 via a trace of rewiring 30.

According to the present embodiment, the traces of the rewiring 30 canbe laid generally straight with a reduction in the wiring length. It isalso possible to suppress variations in the wiring lengths to therespective terminals, i.e., in the resistances and inductances of thetraces. Besides, the rewiring 30 can be laid in a systematic fashion,except those traces of the rewiring 30 to be connected with the solderbumps 20 at the ends of the linear arrangements.

With the layouts shown in FIGS. 3A and 3B, the electrode pads 10 can bearranged linearly in each single area, and thus into a rectangularconfiguration in terms of the entire semiconductor device 100. It istherefore possible to enhance the consistency with conventional designpatterns.

Furthermore, with the layout shown in FIG. 3C, the distances between theelectrode pads 10 and the solder bumps 20 can be made generallyidentical at every location. This can further reduce variations in thewiring length as compared to the layouts shown in FIGS. 3A and 3B. As aresult, it is possible to suppress variations in the circuitcharacteristics of the semiconductor device 100 regardless of whichsignals are associated with which electrode pads 10.

In the present embodiment, each individual area shown by the brokenlines in FIG. 3D may be sectioned in a different configuration such astwo rows by five columns (or five rows by two columns).

THIRD EMBODIMENT

The semiconductor device 100 according to a third embodiment provides amethod of making effective use of the space above a semiconductorintegrated circuit, appearing outside the electrode pads 10 in the firstand second embodiments.

FIGS. 4A and 4B are plan views of part of the semiconductor device 100according to the third embodiment, showing the layouts before and afterpackaging, respectively. As shown in FIG. 4A, before packaging, asemiconductor integrated circuit including the electrode pads 10, afunctional circuit 60, and input/output circuits 70 is formed on the topof the semiconductor substrate 40. The electrode pads 10, the functionalcircuit 60, and the input/output circuits 70 are connected by ordinarywiring 80 inside the semiconductor integrated circuit.

The functional circuit 60 is a functional block for performing signalprocessing in the semiconductor integrated circuit. The functionalcircuit 60 varies in configuration and in area depending on its design.

On the other hand, the input/output circuits 70 are circuit blocks to beconnected with the electrode pads 10 for inputting and outputtingsignals. The input/output circuits 70 include diodes, capacitors, andother protection circuits for protecting the internal circuit elements,and input/output buffer circuits. These protective elements andinput/output buffers are composed of basic blocks which havetransistors, diodes, capacitors, and other elements arranged in apredetermined configuration, with almost fixed sizes.

As shown in FIG. 4B, since the electrode pads 10 are arranged inside theoutermost solder bumps 20, space 420 appears in the peripheral area ofthe semiconductor substrate 40. This space 420 is utilized to arrangethe input/output circuits 70. In the present embodiment, it is desirableto estimate the amount of space to appear outside the electrode pads 10before designing each input/output circuit 70 into a shape to fit inthis space.

According to the present embodiment, the input/output circuits 70 aredisposed to the space 420 above the semiconductor integrated circuit,appearing outside the electrode pads 10. This makes it possible toreduce variations ascribable to the rewiring and decrease the chip sizeof the semiconductor device 100.

Moreover, when the semiconductor device 100 is redesigned to change thefunction or size of the functional circuit 60, the layout of theelectrode pads 10, the solder bumps 20, and the rewiring 30 can be usedintact to shrink the design period.

In digital circuits, it is often the case that the circuit blockconstituting each single unit, such as a gate array, has a fixed circuitconfiguration and a fixed size. Then, such circuit blocks may bedisposed to the peripheral space 420 instead of the input/outputcircuits 70.

The foregoing embodiments have been given solely by way of example. Itwill be understood by those skilled in the art that variousmodifications may be made to combinations of the foregoing componentsand processes, and all such modifications are also intended to fallwithin the scope of the present invention.

The embodiments have dealt with the cases where the solder bumps arearranged in two rows along the periphery of the semiconductor device100. This is not restrictive, however. For example, the solder bumps maybe arranged in two rows along each of two opposite sides out of the foursides of the semiconductor device 100. In this case, electrode pads canbe arranged in the area interposed between the two rows on each side.The embodiments may be applied to one of the four sides alone.

Moreover, even when solder bumps are arranged in any arbitraryconfiguration, such as a matrix of four rows by eight columns and amatrix of eight rows by eight columns, the effects of the presentinvention can be obtained by grouping the solder bumps in two rows andarranging electrode pads therebetween.

Furthermore, the semiconductor device 100 may be configured so thatexternal connection is established via the posts 48 alone, without theformation of the solder bumps 20. An alloy layer may also be formedbetween the posts 48 and the solder bumps 20, or between the posts 48and the rewiring 30, for the sake of preferable electric and physicalconnection properties.

The embodiments are applicable to any of analog circuits, digitalcircuits, and analog-digital hybrid circuits.

While the preferred embodiments of the present invention have beendescribed using specific terms, such description is for illustrativepurposes only, and it is to be understood that changes and variationsmay be made without departing from the spirit or scope of the appendedclaims.

1. A semiconductor device having a wafer level chip size package(WL-CSP) structure, comprising: a semiconductor substrate having anintegrated circuit formed thereon; a plurality of electrode pads formedon the semiconductor substrate, being intended for input and output ofsignals between the integrated circuit and an external circuit; at leastone rewiring layer which includes rewiring formed adjacent to theplurality of electrode pads so as to be integral with the semiconductorsubstrate; and a plurality of external electrodes which is formed on therewiring layer so as to be integral with the semiconductor substrate,the plurality of external electrodes being connected to the plurality ofelectrode pads via the rewiring, the external electrodes makingconnection terminals for the external circuit, wherein the plurality ofelectrodes and the plurality of external electrodes are sectioned andarranged in four areas having the same shapes, corresponding to therespective sides of the semiconductor substrate, wherein each areacomprises: a first group of N number of external electrodes, N being apositive integer, arranged along an edge of the semiconductor substrate;a second group of (N−2) number of external electrodes arranged insidethe first group of external electrodes; and a plurality of (2N−2) numberof electrode pads arranged between the first group of externalelectrodes and the second group of external electrodes, and eachconnected to an external electrode included in either the first group ofexternal electrodes or the second group of external electrodes via therewiring.
 2. The semiconductor device according to claim 1, wherein the(2N−2) number of electrode pads are arranged in a row in parallel withthe edge of a semiconductor substrate.
 3. The semiconductor deviceaccording to claim 1, wherein the (2N−2) number of electrode pads arearranged in two rows in parallel with the edge of a semiconductorsubstrate.
 4. The semiconductor device according to claim 3, wherein, aplurality of electrode pads of the (2N−2) number of electrode pads whichare in the outer row close to the edge of a semiconductor substrate areconnected to a first group of external electrodes, and a plurality ofelectrode pads of the (2N−2) number of electrode pads which are in theinner row far from the edge of a semiconductor substrate are connectedto a second group of external electrodes.
 5. The semiconductor deviceaccording to claim 1, wherein the integrated circuit includesinput/output circuits to be connected to the plurality of electrodepads, the input/output circuits being arranged along the edge alongwhich the first group of external electrodes are arranged such that atleast a part of the circuits overlaps an area where the first group ofexternal electrodes are arranged; and a functional circuit arranged nearthe center of the semiconductor substrate; and the plurality ofelectrode pads are arranged between the input/output circuits and thefunctional circuit, wherein the input/output circuit and the first groupof external electrodes are isolated from each other by an insulatinglayer.